no. 1480. SCHIZOPOD CR VST. 1 ('K. 1 NS—ÓRTMA NN. 43 



the posterior margin. Epimera of the tive anterior segments, with 

 the anterior lappet small, the posterior produced and acutely pointed. 

 There is, on each segment, an indistinct subdorsal keel on each side. 



Epimera of sixth abdominal segment of the type of the second group, 

 formed by only one triangular, acute lappet on each side of the ante- 

 rior section of the segment, and not forming a ventral plate. 



The only difference of the variety sarsi from the typical form is 

 found in the shape of the lamellar expansion of the postero-inferior 

 angle of the carapace: in the typical form, this expansion is rounded 

 oil', while in the variety it is rectangular. It is possible that the latter 

 character is onh r restricted to the young, and that it generali}" disap- 

 pears with advancing age, but then it would disappear at diiferent 

 stages in different individuals, in the average, when they are about 

 half grown (see below). 



The identity of G. zoèa and G. willemoesi — I have devoted much 

 time to the study of the differential characters of these two species, 

 as determined b} r Sars (1885), end have the following to say w T ith ref- 

 erence to them: 



In Sars's synopsis of the species (p. 29), the length of the postero- 

 dorsal spine is paramount: it is "greatly produced" in G. zoèa, and 

 "comparatively short" in G. wiUejnoesi. 



The differences between the species, taken from Sars's diagnosis and 

 description (pp. 38 and 44) are the following: 



1. The length of the postero-dorsal spine just mentioned: in G. zoea 

 this spine reaches sometimes beyond the fourth abdominal segment, 

 while in G. willemoesi it is only slightly longer than the first abdomi- 

 nal segment. 



2. The posterior margin of the carapace, and the margins of the 

 postero-dorsal spine are "coarsely denticulate" in G. zoèa, and 

 "decidedly glabrous" in G. willemoesi. 



3. The rostrum is very elongate (even exceeding the carapace with- 

 out posterior spine), and strongly denticulate in G. zo'ea; it is shorter 

 than the carapace, and provided with small, comparatively few, den- 

 ticles in G. willemoesi. 



4. The spine of the antennal scale projects somewhat beyond the 

 terminal lobe of the lamellar part, and is slightly denticulate at the 

 outer edge, in G. zoèa; it is a little shorter than the terminal lobe, and 

 not denticulate, in G. willemoesi. 



Discussing these four points in detail: 



1. Sars seems to lay much stress upon this character. I have shown, 

 however, in several of the foregoing species, that the relative length 

 of the spines of the carapace changes with age, being generali}^ longer 

 in young individuals. As regards the present case, G. zoea is founded 

 upon specimens much younger than those of G. willemoesi. More- 

 over, 1 have extracted embryos from the marsupial pouch of a large 



